100kHz-30MHz active antenna

 100kHz-30MHz active antenna

 

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The spare radio lover that lives in the city often accepts the restriction of aerial and cannot satisfactory reception in distance, the signal that shortwave broadcasting station transmits. Because performance is good,this is, the medium wave with tall efficiency and shortwave receving antenna not only very long, and what the requirement wears is very tall, and urban building is bristly, can accuse for using very small, consider not to affect the appearance of a city even beautiful wait for a lot of and adverse element with precautionary be struck by lightning so, in wanting to be in inside the urban district outdoor erect ideal, shortwave receving antenna is impossible almost. Radio lover knows, even if the receiver of professional class communication with superior performance, also can be pulled by the antenna with inferior function hind leg. Accordingly, improve aerial to become radio fan people the popular topic that often pays close attention to. 

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   The 100kHz-30MHz active antenna of article introduction conduces to solve a:appellant problem. It has volume small, performance is good, make simple, cost is low wait for a characteristic, what suit to use broadcasting station of Yu Zhongbo and shortwave most is remote receive.

1. circuit 2. Make 3. Use

One. Circuit

 

   If pursue,1 is shown. Q1(MPF102) of canal of effect of high frequency knot field receives source pole to follow implement, the coupling of C1 of classics of radio frequency signal of collect of ANT1 of whip shape antenna arrives its grid. To low frequency signal, c1 has very tall impedance, can restrain the 50Hz of power network and 100Hz hum interference. Neon lamp NE1 drops the electrostatic charge release of aerial induction, because grid accumulates overmuch electrostatic charge,do not send in order to protect Q1 and by puncture. Because this day traditional thread binding is in,this is get together inside chloric second rare conduit, produce very high electrostatic potential because of attrition easily when processing, make aerial induction arrives overmuch electrostatic charge, thereby Q1 of puncture C1 attaint. R1-R3 of bias voltage resistor slants Q1 grid the exports power.Q2 static state electricity that after the MPS3866) of transistor of Q2(UHF of classics of radio frequency signal that to 2.5V.Q1 source pole outputs magnifies, buy provides 100mW for load is 30-40mA about, good linear can maintain when processing big signal.

   Receive blast off in Q2 extremely the gain that medium potentiometer R5 uses circuit to mediate this antenna, slide with its upright paralell connection has the effect that communicates bypass to C3. When R5 mediation arrives not by the position of C3 bypass when, the voltage gain of Q2 is the smallest, its value is 6 times about, right now aerial arrives 2 times of the total gain of cable. When considering impedance inside, the output gain of this circuit should mediate weak signal to receive the result for 36dB.R5 about optimal with lowest useful gain position, in order to hold optimal and dynamic range.

   T1 is to be circled in annular ferrite the broadband transformer on magnetism core, it decides the bandwidth of this aerial amplifier has the effect that matchs to impedance, its are whole winding and the impedance of 1/3 tap part are compared is 9:1. View the past from Q2 collector. The 50-70 ohmic impedance that aerial input carries by Q1, q2 is changed into 450-680 ohm, t1 changes this impedance into 50-75 ohm again, so that be in at receiving,the implementation of receiver input impedance of J1 of output electrical outlet matchs. Resistor R6 restrains the parasitism oscillation that Q2 may appear. Voltage of direct current source passes the capacitor of communication ground connection of T1 Leng Duan.

   Of this amplifier - 3dB bandwidth is 10MHz about, the gain of its frequency high end is inferior, and the gain of low end is taller. This as it happens accords with a requirement. Because the frequency in the antenna below more high frequency rate is taller, what want gain inferior. Especially 12MHz and 15Mhz shortwave broadcasting station sometimes signal is very strong, can cause intermodulation, the gain of aerial amplifier is unfavorable and exorbitant. In 1MHz one, the signal of aerial collect is weaker, right now requirement amplifier provides taller gain. The low rate carrying frequency of this amplifier basically depends on T1, it is about near 80Hz, because this can enclothe the wave band of 140-425 long wave of AM broadcast.

   Graph 1 in the circuit outfit inside dotted line casing is in screen box, the radio frequency signal that the.J1 of circuit of idolum power supply that they are aerial amplifier outputs sends J2 through cable of coaxial of one aspect of the matter, arrive via C4 coupling again receive the receiver in J3. The tension of 13V direct current source that is increased in J2 is passed same paragraph of coaxial cable and J1 are aerial amplifier power supply, c4 cuts off this volts d.c. to make its cannot enter receiver antenna input. The 12-14V alternating voltage of sub output adds transformer of source of small-sized wall electrify to socket PL1, via diode D1 half commutate is mixed R7, r8, c5, get.C7 of voltage of 13V direct current source has bypass effect after C6 filter wave.

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2. Make

   The making cent of this project is aerial amplifier and box of direct current source two parts. The printed circuit that the circuit installation of aerial amplifier shows 2 times in the graph board go up, should the dimension of circuit board is 79.5*19mm, graph 3 it is its component assembly drawing.
 


   Transformer T1 introduces 3 lines and circle a law to be circled in the diameter to go up for the ferrite magnetism annulus of 12.7mm, specific if the graph is shown 4 times,wind a way. Wring ¢ 0.2mm enamel-insulated wire together first, to prevent to receive a fault, can be beforehand on the two end besmear of every line color mark. If graph 4A place is shown, wind 3 strings that wind together on magnetism annulus to circle 508 millimeter to grow (the length) that shows place circles lead, the two end of every lead leave 38.1mm to grow each as down-lead. Next, place of the 4B that press a plan is shown, 6 down-lead of winding from beginning to end join rises, namely the head end that the tail end of a line receives 2 lines, the tail end of line of impending;2 mark receives its contact the head end of 3 lines, its contact uses as the head end of line of tap;1 mark and 3 tail end of the line use as respectively the hot end of transformer and ground connection end. If 3 lines did not do color to label, the test has with avometer after been circle, find out their respective head end and tail end, press graph 4B join next.



   The element of other of transformer along with that will winded shows solder 3 times to be on circuit board by the graph. To assure function, to Q1, q2, NE1 had better not use substitute, also do not revise T1 circle make data. After circuit board solder is good, can consult graph the 5 structures that have aerial amplifier are assembled.

   If the graph is shown 5 times, will have flange dish J1 uses connector of F coaxial cable two screw and spacer secure diameter 19mm inside to get together chloric second is rare on the fender of tracheal connect interior, in will the signal output of circuit board carries solder to arrive the core line of J1, the circuit of this end board ground wire Copper Foil criterion solder arrives the flange of J1 dish, make circuit board firmly originallies to be surely on J1.

   The signal collect line of this antenna uses a diameter 0.8 or the naked steel wire of 1.8 or enamel-insulated wire, one of upright solder are in aerial amplifier board input end, another end secures the box in aerial coping in. The length of signal collect line is decided according to particular him case by everybody, general and desirable for 0.4-0.6mm. If there is catapult near abode, can shorten appropriately its length, but length shoulds not be short at 0.3m, the function when receiving weak signal otherwise becomes poor. This aerial 1.23m is used in weak signal area, grow to cannot improve performance not only again, still can move gain in R5 when the least place still the interference reputation with bigger audibility or noise, can try to change the installation position of aerial, desiccate faze and noise are hit the smallest.

   After the length of signal collect line is affirmatory, consult graph 5 spend with one end length proper, of external diameter 19mm get together cover of chloric second thin tube is outside circuit board, one of end are twisted of J1 get together connect of chloric second rare conduit, another end outfit is in an identical tracheal connect, make signal collect line is worn from latter piece. Twist a 12.7mm to this connect coping next to 19mm turn receive contact, so that give signal collect the clue,install external diameter 12.7mm get together chloric second rare bushing. The length that the length of this bushing inspects signal collect line and calm. Finally, originally top of signal collect line closely to be twisted on the upper cover of bushing with screw cap on coping. Whole antenna part makes a success namely. Attention, all and tracheal, contact and their fastener wants to use white or gray get together chloric second scarce goods and the PVC that does not want black or ABS are plastic, because latter is likely because of contain carbolic element dye and produce high frequency loss. Of course, cannot use a metal more will replace them. Additional, should notice to maintain juncture sealed, prevent rainwater to enter aerial interior, can be in use PVC fluid sealant in contact when necessary.

   Box of direct current source does not use circuit board, use hard line to join means outfit is in small box of a metal however, if pursue,6 are shown. Because the aerial circuit here needs screen, reason must not use metalloid small case. The installation position of direct current source is not significant, can put in any convenience, but above of 0.6m of circuit of report of best distance town, lest communicate interference.

3. Use

   Graph 7 it is active antenna, the join of box of direct current source and receiver pursues. 3 person with coaxial cable join rises, the specific requirement that can inspect an environment will is as long as the person that the cable of 152m receives the occasional in active antenna and box of direct current source is box of direct current source and receiver between, the 12-14V alternating current source of sub output adds transformer of wall electrify source in socket PL1. Active antenna is usable get together chloric second thin tube is propped up go up in the balcony.

   When be used at urban district when this antenna or causing overload box easily to produce the receiver that the holiday answers, had better be lest signal is too strong,jump R5 to gain lowest position. If be to be in a mountainous area country that is far from broadcasting station of puissant AM broadcast to use, move R5 the 1/2 of the biggest gain to 2/3 can.
Attention: Bad Mei Meiji of Jiu Yu Bu installs delay  to band harmonious delicacy falls? of inn of mail of Qian commonplace Fu has; of danger getting an electric shock to also do not get user catapult otherwise, can damage otherwise aerial amplifier and catapult.

   If you have a few receiver, can consult graph 8 make an antenna alloter, install it in metallic screen box, coaxial cable receives reoccupy to input end in box of direct current source and each receiver antenna between, make a few receiver common this antenna. Graph the numeric box computation that 8 medium subordinate list gave out to allocate resistor each is formulary. It is not important that the characteristic impedance of coaxial cable is here, 50 all perhaps can use of 75 ohm, but if length exceeds 30m, had better use the coaxial cable with high grade small loss

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